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is sampled, the real audio level may have gone above the maximum peak level in between samples. True Peak Level is designed to measure that real level. It’s important because broadcasters send their audio through various pieces of equipment which convert from D to A and back, and so during the conversions limit- exceeding peaks may be introduced, causing clipping. Converting from one codec to another may also introduce clipping. True Peak readings give better confidence that this will not happen. Finally, LRA is a measurement of loudness range and this is only a useful measure on a longer piece of audio to give a reading of the difference between the main quieter and louder sections. This is very much a context-based measurement: cinema transmissions may have a value of 25, 20 or 15 LKs, but 20 would be way too much for television, where 15 to 5 would be appropriate. How do I set my brick wall limiter to be safe enough? Are there any PPM or QPPM equivalents? People who use brick wall limiting (very high ratio and fast attack times) to stay within peak level still may go above true peak level, and in fact the more you drive the brick wall, the more you are likely to produce True Peak Level clips. It’s impossible to set a brick wall to be safe enough and while you can get round this by using PPM or QPPM to add an extra margin as a safety net, this artificially limits the freedom you have in mastering. So the idea of the True Peak Level is that it allows more of the headroom to be used without the danger of introducing clipping. What do current audio measurement tools provide for measuring and correcting loudness? The tools from NUGEN Audio give an objective evaluation of the loudness ASK OUR EXPERTS The output log from VisLM-H graphed in Excel, showing various loudness parameters against system time. according to how the ear perceives it. This is important because most audio measurement tools measure how loud the sound seems to the computer measuring it. To the ear, shouting can seem louder than a gunshot because it’s more sustained, for example. For dialog clarity you could specify the minimum number of loudness units the dialog needs to be louder than the soundtrack, as an internal objective check listening subjectively and mixing on a high quality studio system, because the perceived separation may not be there on the small speakers in a consumer TV NUGEN Audio produces a range of real time editor-based and file-based loudness analysis and correction tools, appropriate for scenarios from solo production engineers through ingest and right into broadcast edit suites. The products are designed to make the sometimes complex issues of loudness metering easier to negotiate, with intuitive solutions to get the problems solved rapidly. VisLM provides visual loudness metering with history and logging, standalone or editor-based plugin. LMB (Loudness management batch processor) is an automated file-based analysis and correction application. LMCorrect, an Avid editor based correction for ProTools and MediaComposer, provides analysis and automated correction. The choice of tool depends on the scenario: VisLM provides detailed analysis and is a mixing tool that can be used in real time to understand the loudness make up of POST YOUR QUESTION ONLINE: Search ‘tvbay’ your audio, while LMcorrect is more of a compliance tool. What emerging trends are there? The introduction of loudness standards has suddenly focused attention on audio quality in general, so other aspects of audio are now coming under the spotlight. Hyper-compression and unnecessary limiting is one of these. Much of the reason why adverts often appear so loud on television is because of the hyper-compression. It’s a quality issue – advertisers all wanted their ads to be louder than everyone else’s. Now we should start to see much more attention paid to quality. Loudness range is objectively measurable with LRA, so we will be able to investigate situation sensitive dynamic range considerations: for example if you are sitting with your 5.1 system at home and everyone is quiet, you can have a very wide dynamic range. But if you are watching a podcast on the train, you need a low dynamic because of the background noise. These are all new possibilities opened up by loudness parameters. Another new trend will be the increased examination of surround sound and upmixing. The whole question of audio continuity is also likely to be raised to address the continuity of background noise and transitions between programs. There’s a lot of opportunity to look at how the industry can make better audio. Tel. +44 (0)1635 237 237 Email. questions@tv-bay.com TV-BAY MAGAZINE | 47 TV-BAY067JUL12.indd 47 05/07/2012 22:24